分类： 生物学 >> 生物进化论 提交时间： 2024-03-21
摘要： The affinity of ‘Dongfangaspis qujingensis’, initially assigned to Dongfangaspisbut later to Laxaspis, has long been controversial. However, the taxonomical revision raisesa new problem of junior homonym since the type species of Laxaspis is L. qujingensis. Here,we describe some new materials of ‘Dongfangaspis qujingensis’ and Damaspis vartus fromthe Xishancun Formation (early Lochkovian, Early Devonian) in Qujing, Yunnan Province.‘Dongfangaspis qujingensis’ strikingly resembles Damaspis vartus in the slightly longerheadshield, bifurcated ends of the lateral transverse canals, unconnected V-shaped posteriorsupraorbital canals, and at least seven pairs of lateral transverse canals issuing from the lateraldorsal canal. These similarities indicate that ‘D. qujingensis’ is more suggestive of Damaspis thanDongfangaspis and Laxaspis. Therefore, we propose to remove ‘Dongfangaspis qujingensis’ fromLaxaspis to Damaspis. The new specimens of Damaspis vartus reveal five long lateral transversecanals on the right side, corroborating that the asymmetric sensory canal system in the holotype isthe intraspecific variation.
分类： 生物学 >> 生物进化论 提交时间： 2024-03-20
摘要： Here we report a new form of amphicyonid from an uncertain locality in the LinxiaBasin. The derived dental traits imply an affinity to Magericyon, previously known from Europe and possibly southern Asia. The specimen suggests a higher diversity of amphicyonids in eastern Asia than previously thought, and more discovery with stratigraphic information will be needed to elucidate the evolution of Amphicyonidae in eastern Asia.
分类： 生物学 >> 生物进化论 提交时间： 2024-03-15
摘要： The previously alleged ‘eugnathid amiiform’ Sinoeugnathus kueichowensis is asmall-sized halecomorph from the Middle Triassic (Ladinian) marine deposits of Guizhou andYunnan, China. A morphological redescription and taxonomic revision of this taxon are providedbased on a detailed examination of 15 new specimens. Among them, IVPP V24315 (standardlength = 64 mm) is appointed as the neotype, given that the holotype is missing. Studies of thesespecimens revealed some morphological details previously undescribed or misidentified forthis taxon, including a hatchet-shaped antorbital, two broad suborbitals, a sensory canal in themaxilla, and three pairs of extrascapulars. For the first time, Sinoeugnathus was incorporatedinto an analysis of halecomorph phylogeny, and the results recover it as the sister taxon of theAnisian Subortichthys from Luoping, Yunnan, and both are grouped with two Ladinian generaAllolepidotus and Eoeugnathus from the Monte San Giorgio area into a monophyletic group(namely Subortichthyidae fam. nov. herein) at the base of Ionoscopiformes. This taxonomicreassessment of Subortichthys provides new insights into the phylogeny and paleogeographicevolution of Ionoscopiformes.
分类： 生物学 >> 生物进化论 提交时间： 2024-03-15
摘要： All the extant rhino species belong to Rhinocerotini and either have one horn (a nasal horn) or two horns (a nasal horn and frontal horn). So far, the earliest Rhinocerotini to have been identified in China is the “Dicerorhinus” cixianensis, which was based on a juvenile skull with an associated mandible from the Middle Miocene locality of Jiulongkou in Cixian County, HebeiProvince of northern China. Our analyses suggest that there are similarities between this specimenand the modern genus, Dicerorhinus, but it differs in several cranial traits and therefore cannotbe assigned to the modern genus. Instead, it is closer to the Middle Miocene Lartetotheriumfrom Europe, especially the specimen from La Retama in Spain and should be assigned to thatgenus, indicating the presence of intracontinental dispersal at this time. The Jiulongkou faunais the only Middle Miocene fauna with Rhinocerotini in China, and, together with the faunalcomposition, this implies a more humid and closed environment, in contrast to those found inwestern China. We suggest that the position of the posterior border of the nasal notch is a goodindication of the specimen’s evolutionary level in Rhinocerotini. The anterior position of the nasalnotch as seen in modern Dicerorhinus, together with its certain similarities to L. cixianensis aswell as its differences with more specialized species of the Dihoplus-Pliorhinus-Stephanorhinus-Coelodonta lineage, supports the conclusion that Dicerorhinus experienced little change during anearly 10 Myr evolutionary history, possibly due to the low selection pressure seen in the tropical/subtropical forests in southeastern Asia.
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